Differences between sexes and hand-
specific use in manual motor function: an
impression of Fitts’ law
, 1. Introduction
Hand-eye coordination follows laws. In this study the specific type of hand-eye coordination
that is studied is pointing at displayed targets. The law fitting this type of hand-eye
coordination is Fitts’ Law. Fitts’ Law states that the larger the target, and the nearer it is to the
starting point, the faster it can be pointed to [1].
With his law, Fitts compared the capacity of the motor system with the capacity of a
communication channel. In the human body, the motor system would consist of the muscles,
nerves and control mechanisms. In experiments it is important that the movement that is to be
made, is as simple as can be, to eliminate the problem that the information channel cannot
process fast enough. The motor system is only as fast as the information channel. Therefore,
the observed result is always the result of the total system of receptors, neural channels and
effects, and if the information channel cannot process fast enough it affects the rest of the
system so the maximum capacity cannot be measured [2]. The method of measuring is based
on this principle: pointing at displayed targets, first with the dominant hand and then with the
other hand.
Fitts summarized the relationship between target size, distance and placement time in the
formula:
D
T =a+ b ∙ log 2 (1+ )
W
T is the time to move, D is the distance and W is the width of the target along the direction of
movement of the pointer. Because D is divided by W it can be concluded that when D
increases, T increases as well, but when W increases, T decreases [1].
What determines which hand is the dominant hand or that there is no preference at all? This is
based on the two hemispheres in the brain and the phenomenon called laterality. What is
important to know is that the left hemisphere controls the right side of the body and the right
hemisphere the left side of the body. The concept of laterality is based on the finding that
most changes are caused by spontaneous violation of symmetry. Laterality causes a violation
in symmetry in the hemispheres, causing the preference of one body side over the other. This
preference is caused because one hemisphere is larger and thus more developed than the other
2
specific use in manual motor function: an
impression of Fitts’ law
, 1. Introduction
Hand-eye coordination follows laws. In this study the specific type of hand-eye coordination
that is studied is pointing at displayed targets. The law fitting this type of hand-eye
coordination is Fitts’ Law. Fitts’ Law states that the larger the target, and the nearer it is to the
starting point, the faster it can be pointed to [1].
With his law, Fitts compared the capacity of the motor system with the capacity of a
communication channel. In the human body, the motor system would consist of the muscles,
nerves and control mechanisms. In experiments it is important that the movement that is to be
made, is as simple as can be, to eliminate the problem that the information channel cannot
process fast enough. The motor system is only as fast as the information channel. Therefore,
the observed result is always the result of the total system of receptors, neural channels and
effects, and if the information channel cannot process fast enough it affects the rest of the
system so the maximum capacity cannot be measured [2]. The method of measuring is based
on this principle: pointing at displayed targets, first with the dominant hand and then with the
other hand.
Fitts summarized the relationship between target size, distance and placement time in the
formula:
D
T =a+ b ∙ log 2 (1+ )
W
T is the time to move, D is the distance and W is the width of the target along the direction of
movement of the pointer. Because D is divided by W it can be concluded that when D
increases, T increases as well, but when W increases, T decreases [1].
What determines which hand is the dominant hand or that there is no preference at all? This is
based on the two hemispheres in the brain and the phenomenon called laterality. What is
important to know is that the left hemisphere controls the right side of the body and the right
hemisphere the left side of the body. The concept of laterality is based on the finding that
most changes are caused by spontaneous violation of symmetry. Laterality causes a violation
in symmetry in the hemispheres, causing the preference of one body side over the other. This
preference is caused because one hemisphere is larger and thus more developed than the other
2
